| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Original Report |
1 Instituto de Radiologia, Hospital das Clinicas da Faculdade de Medicina da
USP, São Paulo, Brazil.
2 Instituto Israelita de Ensino e Pesquisa Albert Einstein, Department of
Radiology, Albert Einstein Hospital, São Paulo, Brazil.
3 Department of Cardiothoracic Surgery, Harvard Medical School, Beth Israel
Deaconess Medical Center, Boston, MA 02215.
4 Department of Radiology, Harvard Medical School, Beth Israel Deaconess Medical
Center, 330 Brookline Ave., Boston, MA 02215.
Received January 24, 2004;
accepted after revision August 10, 2004.
Address correspondence to P. M. Boiselle.
Abstract
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
CONCLUSION. Five patients were referred for dynamic MDCT before and
after undergoing tracheoplasty at our institution. Preoperatively, all
patients showed signs of tracheobronchomalacia (
50% airway collapse) on
bronchoscopy, and four (80%) of these five patients showed evidence of malacia
on dynamic forceful expiratory CT scans. In all five cases, postoperative CT
showed a reduction in the degree of airway collapse during expiration, changes
in shape of the trachea during inspiration, and posterior wall thickening
related to the procedure. Our preliminary results suggest a potentially
important role for CT in the pre- and postoperative assessments of patients
with tracheobronchomalacia referred for tracheoplasty.
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The treatment of tracheobronchomalacia is variable and depends on the severity of symptoms. In patients with severely symptomatic tracheobronchomalacia due to excessive flaccidity of the posterior membranous portion of the airway wall, surgical intervention can be curative and is considered the treatment of choice [4]. The surgical procedure is referred to as "tracheoplasty" and consists of surgical plication of the posterior wall of the central airways using a graft sutured to the posterior membranous portion [4]. The goals of the surgery are to reshape the trachea, increase its rigidity, and decrease its collapsibility [4].
To our knowledge, the CT findings in patients undergoing this procedure have not yet been described. We report the pre- and postoperative CT findings in a series of consecutive patients who underwent tracheoplasty at our institution. We also briefly describe the technical aspects of this surgical procedure.
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
All patients underwent the same CT protocol for both pre- and postsurgical examinations on an 8-MDCT scanner (LightSpeed, GE Healthcare) with a gantry rotation time of 0.5 sec. The CT protocol focused on the central airways—from the thoracic inlet to approximately 2 cm below the carina—and included imaging during two phases of respiration: end-inspiratory and dynamic expiratory phases. The end-inspiratory helical scan (170 mAs, 120 kVp, 2.5-mm collimation, high-speed mode, and pitch equivalent of 1.5) was obtained first in all patients and was followed by a dynamic expiratory low-dose helical scan (40 mAs, 120 kVp, 2.5-mm collimation, high-speed mode, and pitch equivalent of 1.5) in which the patient was instructed to forcefully exhale during CT acquisition. The dynamic expiratory component of the CT scan was completed in approximately 5 sec.
Our hospital institutional review board approved the review of radiologic and clinical data for this study. Informed consent was not required for this retrospective analysis, but patient confidentiality was protected. All CT scans (pre- and postoperative inspiratory and expiratory images) were jointly reviewed by consensus by two experienced thoracic radiologists on a PACS workstation (Centricity version 2.0, GE Healthcare) for several parameters.
The first parameter was quantification of the percentage of airway luminal collapse during expiration for the levels of the trachea, carina, and each mainstem bronchus; this was performed by using an analysis tool available on our PACS software to measure the cross-sectional area of the airway lumen in millimeters squared on end-inspiratory and dynamic expiratory scans. We calculated the percentage of luminal collapse by dividing the dynamic expiratory cross-sectional area by the end-inspiratory cross-sectional area and multiplying by 100. The second parameter was the shape of the trachea. The reviewers noted whether the trachea was round, oval, horseshoe, biconvex, or lunate given that round, oval, and horseshoe shapes are considered normal tracheal configurations [5, 6]. The third and fourth parameters were presence or absence of tracheal wall thickening (defined as wall thickness > 3 mm [7]) and the presence or absence of associated lung or mediastinal disease.
With regard to measurement of the airway lumen, cross-sectional area measurements were performed by an experienced radiologist using an electronic tracing tool, and individual measurements were agreed on by consensus review by a second radiologist. Our methodology did not involve averaging of slices because we used only a single axial CT image with the greatest airway collapse at dynamic expiration for each level of analysis (trachea, carina, and mainstem bronchi) and compared it with the respective axial image level at end-inspiration. Postoperative scans were also assessed for specific complications, including airway dehiscence, mediastinal hematoma, abscess, and pleural effusion or pneumothorax.
The percentage of reduction in the degree of airway collapse, from the preoperative to the postoperative studies, was also calculated for all five patients.
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
All five patients showed evidence of tracheobronchomalacia at bronchoscopy, and four (80%) of five showed evidence of tracheobronchomalacia on preoperative dynamic CT. One patient (patient 4 in Table 1) who has severe asthma was unable to fully cooperate with the expiratory breathing instructions, resulting in a false-negative CT scan.
The mean percentages of airway collapse at dynamic expiration on preoperative scans were 57.6%, 59.2%, 53.1%, and 65.8%, respectively, for the levels of the trachea, carina, right mainstem bronchus, and left mainstem bronchus. For the scans obtained after tracheoplasty, the mean percentages of airway collapse, for the same respective levels, were 23.6%, 24.8%, 29.9%, and 29.1%.
With regard to the shape of the trachea on preoperative CT studies, three (60%) of the five patients presented with a biconvex or "fishmouth" tracheal shape at end-inspiration; four (80%) of five patients had a convex anterior–concave posterior or lunate tracheal shape at dynamic expiration. The only patient whose trachea did not exhibit a lunate configuration at dynamic expiration was the patient who was unable to fully cooperate with expiratory breathing instructions (patient 4). Conversely, after tracheoplasty, all five patients showed a normal tracheal shape at end-inspiration, and four (80%) of the five patients also showed a normal tracheal shape at expiration (Fig. 1A, 1B, 1C, 1D).
|
|
|
|
We observed posterior airway wall thickening (> 3 mm) [7] on CT scans of all five patients after tracheoplasty, an expected finding because the posterior airway wall is folded and reinforced with a graft (Fig. 2A, 2B). The average thickness of the posterior wall after surgery was 5.4 mm (range, 5–6 mm).
|
|
In one patient who was imaged 4 days after the operation for a suspected surgical complication, we observed heterogeneous soft-tissue density surrounding the trachea and esophagus that corresponded to edema and hemorrhage; the surgeon considered these early postoperative findings to be normal. The patient showed a good clinical recovery and later underwent another CT study 45 days after surgery, which showed complete resolution of those early postoperative findings (Fig. 3A, 3B).
|
|
In clinical follow-up, all five patients reported subjective improvement of symptoms after the surgical procedure. None of the five patients experienced a significant complication from the procedure.
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The treatment of tracheobronchomalacia is variable, ranging from clinical follow-up for incidentally discovered, asymptomatic cases to various types of intraluminal airway stenting and surgical procedures for symptomatic cases. In the past, aortopexy was the routine procedure for the surgical treatment of this condition [11]. This procedure consists of attachment of the anterior wall of the aorta to the undersurface of the sternum, thus providing sufficient space in the mediastinum so that the malacic tracheal segment would not be compressed by adjacent structures [11]. However, because this procedure does not directly treat the malacic segment, airway collapse may still occur during expiration and coughing.
The first article describing a tracheoplasty procedure was written by Herzog and published in 1954 [12]. This procedure has recently received renewed attention for its role in treating symptomatic tracheomalacia in adults [4]. Herzog initially used bone grafts to increase the rigidity of the membranous wall of the trachea [12]. Approximately one decade later, Rainer et al. [13] altered the approach by imbricating the posterior membranous tracheal wall with a polypropylene sheet. More recently, the technique has been further modified by plicating the posterior membranous wall with Marlex mesh [4].
In our institution, a right posterolateral thoracotomy approach is used for tracheoplasty, and the posterior membranous wall of the trachea and main bronchi are dissected to expose the airway. Marlex mesh is fashioned into a 2.0-cm-wide strip and sutured to the posterior membranous wall, reinforcing it. The graft is usually placed proximally from the level of the thoracic inlet and distally to the level of the mainstem bronchi. This procedure is offered to patients with severely symptomatic diffuse tracheobronchomalacia who are good surgical candidates and in whom a trial of central airway stenting has resulted in improved clinical symptoms. It is important to note that the use of long-term metallic stents in patients with diffuse tracheobronchomalacia should be avoided because of an increased risk of stent fracture due to changes in airway size and shape during respiration [14]. Silicone stents are preferable to metallic stents for treating malacia and also have the advantage of being easily removable [14].
Our results show that tracheoplasty resulted in a decrease in the degree of airway collapse in all five patients with postsurgical CT scans. Importantly, this quantitative improvement was accompanied by a qualitative improvement of respiratory symptoms. Changes in the tracheal shape resulting from the surgical procedure were also clearly verified by CT. Before surgery, the trachea was biconvex (fishmouth) at end-inspiration in 60% of the patients, and it was lunate at dynamic expiration in 80% of the patients. This appearance can be explained by the pathophysiology of the disease: The flaccid posterior membranous wall of the trachea bows anteriorly during dynamic expiration in response to elevated intrathoracic extratracheal pressure [15]. Surgical reinforcement of the posterior membranous wall with tracheoplasty enhances the rigidity of this structure and makes it less susceptible to bowing during expiration. After tracheoplasty, 100% of the patients showed a normal-shaped trachea at end-inspiration and 80% showed a normal-shaped trachea at dynamic expiration.
We realize that there are limitations regarding the use of dynamic CT for evaluating tracheobronchomalacia, particularly because this technique relies on the ability of the patient to cooperate with breathing instructions. For example, this factor was the cause for the one false-negative preoperative CT study in this series, which occurred in a patient with severe asthma. However, we emphasize that all other cases in our study showed a good correlation between dynamic expiratory CT and bronchoscopy; moreover, a good correlation between dynamic CT and bronchoscopy has also been described in the literature [3].
We also realize that there is a potential for measurement error in our methodology. We emphasize that the consensus review of measurements by a second radiologist limited the potential for measurement error in our study. We did not attempt to validate the cross-sectional area measurements of the airways obtained with our tracing software by comparing them with phantom measurements because these methods have been previously validated by other authors using similar measurement software programs [16].
Despite these limitations, we have found that CT plays several potentially important roles in the pre- and postoperative settings. Its preoperative roles include the precise characterization of airway shape and determination of which parts of the airway wall contribute to excessive airway collapsibility. For example, patients with a lunate trachea at expiration are considered excellent candidates for tracheoplasty because this configuration implies that a redundant, "floppy" posterior membranous wall is the major factor contributing to the excessive airway collapse [4]. Thus, reinforcing the posterior membranous wall with a graft is likely to correct malacia in these patients. On the other hand, patients with normal posterior membranous walls and excessive collapsibility of other airway wall components (anterior, lateral) are unlikely to benefit from this procedure. The second role of preoperative CT is the evaluation for airway wall thickening and calcification. In combination with airway malacia, these findings suggest polychondritis, a disorder that is not treated surgically. The third role of preoperative CT is the evaluation for extrinsic paratracheal masses, which may preclude surgery. Finally, preoperative CT scans can serve as a baseline measure of airway collapsibility with which to compare postoperative scans for evaluating response to surgery.
In the postoperative setting, CT provides a noninvasive method for assessing for postoperative complications and noninvasively quantifying the degree of improvement in airway collapsibility. With regard to the time interval for obtaining a CT scan postoperatively, as observed in one of our patients, CT scans in the early postoperative period (Fig. 3A, 3B) can show transient postoperative changes in the mediastinum, such as fluid and blood, that should not be considered as complications related to the procedure. We thus recommend a minimum delay of 1 month after surgery before a final evaluation of the surgical results can be achieved. Obviously, if there is a concern for a postoperative complication, CT can be performed earlier. Finally, CT has the unique ability to visualize the characteristic thickening of the posterior wall of the airways after surgery, a finding observed in all our patients. This finding may serve as a clue for one to suspect that tracheoplasty has been performed.
In our preliminary experience, our surgeons and pulmonologists have found a combination of subjective symptomatic improvement and quantitative reduction in airway collapsibility on CT to be the most helpful measurements of determining response to surgery. Because not all patients in our study population underwent pre- and postoperative pulmonary function tests, we did not attempt to compare CT findings with pulmonary function test results. Future studies comparing CT and pulmonary function tests will be necessary to determine the precise contribution of these methods to determining response to therapy.
In conclusion, dynamic expiratory CT is a potentially valuable tool in the pre- and postoperative evaluations of patients undergoing tracheoplasty, a novel surgical method that is increasingly being used for the definitive treatment of patients with severely symptomatic tracheobronchomalacia.
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
This article has been cited by other articles:
|
|
 |
|
  S. H. Loring, C. R. O'Donnell, D. J. Feller-Kopman, and A. Ernst Central Airway Mechanics and Flow Limitation in Acquired Tracheobronchomalacia Chest, April 1, 2007; 131(4): 1118 - 1124. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
